Mobile communications systems include earth-to-space satellite links, communications involving high speed aircraft and other types of communications systems in which a receiver moves relative to a transmitter. The relative movement of the receiver to the transmitter may cause an effective change in frequency of the received signal. This effective change in frequency is known as the Doppler effect. The Doppler effect must be rectified in order to achieve efficient data transmission and reception.
A standard technique for Doppler correction is to use frequency-tracking loops. Frequency-tracking loops usually require substantial time for acquisition. Additionally, frequency-tracking loops have a limited lock-in range and can only handle relatively small Doppler offsets. Moreover, frequency-tracking loops invariably work only in passband, and thus do not correct for other transmission defects besides Doppler.